Definition: You are given a question on high school government and politics. You are also given 4 answer options (associated with "A", "B", "C", "D"), out of which only one is correct. You need to answer the question by selecting the correct option. You should only answer with the choice letter, not the whole answer.
Input: Which of the following is the largest source of "automatic spending" for the federal government?
(A)Salaries to employees of the U.S. Post Office (B)Interest payments made to U.S. bondholders (C)Entitlement programs (D)National defense

C